1. Field of the Invention
The present invention relates to mechanical seal assemblies for pumps. More particularly, the present invention relates to an improved mechanical pump seal assembly that includes a specially configured seal cartridge enabling standard O-rings to be used instead of specially configured Teflon® seals and that can be used as a retrofit for existing mechanical seal assemblies associated with pumps such as barge pumps.
2. General Background of the Invention
An example of a mechanical seal assembly is shown in the U.S. Pat. No. 4,648,605 issued to Joseph Marsi and entitled “Mechanical Seal Assembly”. The '605 patent discloses a mechanical seal assembly especially adaptable for use in the chemical industry in which a jacket that is impervious to the chemical involved surrounds a spring which urges seal faces toward one another, the spring being capable of transmitting torque and providing axial support to the jacket.
At the Flowserve website (www.flowserve.com), a number of pump sealing arrangements are displayed. The home page for seals is www.flowserve.com/Seals/seals.htm. One of the seals disclosed at the website is called a “UC” seal. The UC seal is designed for corrosive/non-corrosive high pressure services with a specific gravity of 0.45 or higher. The canned “UC” seal design incorporates a high pressure design feature that is similar to the Flowserve “U” seal while incorporating an encapsulated graphite gasketed silicon carbide rotating face. The UC seal's canned face design provides for low level emissions control.
Borg Warner sells mechanical seals for pumps such as barge pumps under its product designations U2250 and U1875. These seal designs utilize a cylindrically shaped sleeve that fits in between the pump shaft and a seal cartridge that employs a U-shaped cup seal. Over time, the sleeve can be fret damaged by the cup seal.
Fret damage occurs as a result of the original factory Teflon® U-cup moving up and down on the shaft sleeve. The U-cup (when in operation) is inflated by the product being pumped under pressure, thus putting pressure on the shaft sleeve. The Teflon® U-cup under such pressure will scratch the sleeve. These resulting scratches can be described as fret damage. This fret damage can cause leaking of gases to occur through the Teflon® U-cup. In addition, once the pressure is relieved, the U-cup deflates, which can allow leakage of gases through the U-cup, even if it is not fret-damaged.